MANILA, Philippines – The element uranium is most well known for its toxic and radioactive properties, which could be lethal to humans. It has different forms depending on the application, but it is most widely used as nuclear fuel in nuclear power plants.
It recently got public attention when news broke about authorities exposing a syndicate trafficking hazardous uranium. The syndicate was found to be operating in Pasay, Mandaue, and Cagayan de Oro.
Here’s everything you need to know about uranium.
How was it discovered?
Uranium can be found in most rocks on Earth in trace or extremely small concentrations, according to the World Nuclear Association. It can be found in seawater as well, though its extraction from the ocean is subject of an ongoing research.
The element was discovered in 1789 by German chemist Martin Klaproth in the mineral called pitchblende. Klaproth separated uranium out of pitchblende as a black powder, according to the Royal Society of Chemistry (RSC), but in its pure form, the element appears as a silvery white metal. The chemical symbol for uranium is U.
Uranium, in nature, occurs in different forms called isotopes. A bulk of uranium found in Earth’s crust consists of two isotopes — uranium-238 (U-238) accounts for 99.3%, while another isotope, uranium-235 (U-235), accounts for 0.7%.
Both U-238 and U-235 are radioactive, which means they decay and emit radiation in the process. U-238 decays very slowly or is barely radioactive, but the heat it produces is enough to warm Earth’s core. U-235 decays a bit faster or is more radioactive than U-238.
Where is it found?
Uranium can be found in rocks, but extraction can be expensive since concentrations are extremely small. When a rock is concentrated enough with uranium to be mined profitably, it is called an orebody. Uranium reserves are then calculated as tons recoverable up to a certain cost.
Here are the 10 countries with the most uranium resources in 2021, according to data from the World Nuclear Organization.
| Rank | Country | Uranium (tons) | % of world |
| 1 | Australia | 1,684,100 | 28% |
| 2 | Kazakhstan | 815,200 | 13% |
| 3 | Canada | 588,500 | 10% |
| 4 | Russia | 480,900 | 8% |
| 5 | Namibia | 470,100 | 8% |
| 6 | South Africa | 320,900 | 5% |
| 7 | Niger | 311,100 | 5% |
| 8 | Brazil | 276,800 | 5% |
| 9 | China | 223,900 | 4% |
| 10 | Mongolia | 144,600 | 2% |
Uranium orebodies can be mined from open pits or underground excavation sites, according to the International Atomic Energy Agency, after which the ores are crushed and refined to separate uranium from other elements.
This method has been gradually replaced by the now most common method called in situ leaching (ISL). In situ means in the natural or original position or place. In ISL, uranium is dissolved in the deposits and then extracted underground to be refined into uranium oxide or yellow cake, a yellow powder-like substance. It is in this form that uranium is sold.
Nuclear fuel cycle
Nuclear reactors in nuclear power plants mostly use uranium as fuel. Extracted uranium ores go through a series of processes to become nuclear fuel.
Through ISL, ores are turned into yellow cake, which is then processed into uranium dioxide, a black powder-like substance. The black powder is compressed to become uranium pellets, which are inserted into long metal tubes stacked together to make fuel assemblies. The fuel assemblies are the main source of fuel for reactors.
The reactors mainly produce energy from the splitting of uranium atoms into two — a process called fission.
Inside a nuclear reactor, U-235 atoms easily split, which means they are fissile, while U-238 atoms undergo a reaction to become plutonium-239, a plutonium isotope, which splits more easily. When a splitting of an atom causes the splitting of another atom, a fission chain reaction happens. When fission occurs millions of times, a large amount of heat is produced with just a small amount of uranium.
Aside from power plants, military nuclear warheads use uranium fuel as well. Weapons-grade uranium is most times enriched by increasing the concentration of the more fissile isotope U-235 from 0.7% to 90% or higher. Uranium for nuclear reactors is enriched up to only 5% U-235.
Radioactivity and toxicity
The safety of nuclear power plants has been questioned over the years, especially since nuclear accidents have occurred in the past. Two of the most well-known nuclear disasters occurred at the Chernobyl Power Plant in Ukraine in 1986 and at the Fukushima Daiichi Power Plant in Japan in 2011. Thousands of deaths were linked to the disasters.
The radiation that comes from decaying uranium can be lethal to humans if absorbed in huge amounts. According to the United States’ (US) Center of Domestic Preparedness, the dose of radiation would need to be 1,000 gray or higher for death to occur within hours of exposure, and 4 to 5 gray within 60 days.
Uranium itself is also chemically toxic to humans. It can affect organs and body processes when ingested in significant amounts, according to the US Environmental Protection Agency.
The US National Institute of Occupational Safety and Health recommends that exposure to uranium in the air should not exceed 0.05 milligrams per cubic meter for soluble uranium and 0.2 milligrams per cubic meter for insoluble uranium in 10 hours. This mostly applies to people exposed to uranium in the workplace.
Other uses
Uranium comes in more forms for other applications.
When uranium is enriched with U-235, the process produces leftovers called depleted uranium (DU), which is a metal that has a reduced U-235 content. This makes the chemical 40% less radioactive than the naturally occurring uranium, according to chemistry professor Polly Arnold in an RSC podcast.
Different objects like armor-piercing weapons and sailboats use DU for shielding because of its dense property. The metal has the ability to self-sharpen as it pierces through a target or medium.
In glassmaking, uranyl salts “give a very beautiful and translucent yellow-green color to glass.” Although pieces made with uranyl salts are generally safe to drink from, people are advised not to drill holes or wear them down, Arnold said in the podcast.
Uranium also has lesser known applications. Artificially produced radioactive materials or radioisotopes from small special-purpose nuclear reactors have become widespread since the early 1950s, according to the World Nuclear Association.
Radioisotopes have been used in medicine for diagnosis and research, an example of which is radiotherapy in treatment of some illnesses like cancer. They have been used in food preservation and livestock breeding as well.
Uranium in the Philippines
Scientists in the Philippines have also been studying uranium. In 2020, when the government had been considering nuclear energy, nuclear scientists from the Department of Science and Technology (DOST) joined the rest of the world in exploring how to recover uranium from seawater.
“If uranium can be recovered locally from seawater, it may help alleviate costs and importation challenges of nuclear fuel,” Jordan Madrid of the DOST-Philippine Nuclear Research Institute (PNRI) was quoted as saying in a press release.
In 2022, PNRI reopened the country’s sole nuclear reactor training facility in Quezon City. – Rappler.com